Method and apparatus for requesting media replication in a collaborative communication session, and method and apparatus for assigning a communication medium for a collaborative communication session

ABSTRACT

In a method for requesting media replication in a collaborative communication session, a message is sent which specifies that a communication medium for a collaborative communication session, which is currently being transmitted to at least one terminal, should additionally be transmitted to at least one other terminal, with the at least one other terminal being indicated in the message as the recipient of the communication medium. In a method for assigning a communication medium for a collaborative communication session, a corresponding message is received, and the communication medium is assigned to the at least one other terminal as the recipient of the communication medium. The methods are carried out by appropriately designed apparatuses.

The invention relates to a method and an apparatus for requesting mediareplication in a collaborative communication session, and to a methodand an apparatus for assigning a communication medium for acollaborative communication session.

Communication by technical means between a specific, finite number ofsubscribers is referred to as a communication session. A collaborativecommunication session is the process of communicating using a pluralityof communication terminals (also referred to for short in the followingtext as terminals) for a single one of the communication ends. In otherwords, at least one of the communication ends (that is to say one of thesubscribers) uses a plurality of terminals in order to communicate withat least one other communication end. A terminal at one communicationend controls the collaborative session, for example by defining whichcommunication media (for example audio, video, text, etc.) should betransmitted to which terminals in the collaborative session, and ittherefore intrinsically has a so-called control role.

In order to allow the functions of controlling terminals in acollaborative communication session precisely for that controllingterminal (and in particular not to allow them for the non-controllingterminals), it is necessary to be able to allocate (or in other words:assign) the control role for one terminal in the communication system.

It is known from the document “3GPP Technical Specification TS23.237,V9.2.0, IP Multimedia Subsystem (IMS) Service Continuity; Stage 2” thatcollaborative communication sessions (collaborative sessions) can becarried out using a communication system which is designed on the basisof the Internet Protocol Multimedia Subsystem (IMS) of the 3GPP mobileradio standard.

In collaborative communication sessions in the IMS, one user with aplurality of terminals is registered with the IMS. The collaborativesession is set up by one of the terminals requesting the IMS to transferone of its communication media to another terminal of the user. Thismeans that, after the media transfer, the medium is no longer receivedby that communication terminal but by the other communication terminal.In this case, the terminal requesting this media transfer is assignedthe control role for the collaborative session.

Only one holder of the control role can subsequently control thecollaborative session and, for example, carry out further mediatransfers. In the case of IMS collaborative communication sessions, thecontrol role is always assigned to that terminal which requests thefirst media transfer.

It would be desirable to allow a collaborative session to be controlledin a more flexible manner.

The problem is solved by the methods and the apparatuses according tothe respective independent patent claims.

In a method for requesting media replication in a collaborativecommunication session, a message is sent which specifies that acommunication medium for a collaborative communication session, which iscurrently being transmitted to at least one terminal, shouldadditionally be transmitted to at least one other terminal, with the atleast one other terminal being indicated in the message as the recipientof the communication medium.

Media replication can also be described by the terms media copying,media modeling or media copy.

An apparatus for requesting media replication in a collaborativecommunication session has a transmitting unit which is designed to senda message which specifies that a communication medium in a collaborativecommunication session, which is currently being transmitted to at leastone terminal, should additionally be transmitted to at least one otherterminal, with the at least one other terminal being indicated in themessage as the recipient of the communication medium.

In a method for assigning a communication medium for a collaborativecommunication session, a message is received which specifies that acommunication medium for a collaborative communication session, which iscurrently being transmitted to at least one terminal, shouldadditionally be transmitted to at least one other terminal, with the atleast one other terminal being indicated in the message as the recipientof the communication medium, and the communication medium is assigned tothe at least one other terminal as the recipient of the communicationmedium.

An apparatus for assigning a communication medium for a collaborativecommunication session has a receiving unit which is configured toreceive a message which specifies that a communication medium for acollaborative communication session, which is currently beingtransmitted to at least one terminal, should additionally be transmittedto at least one other terminal, with the at least one other terminalbeing indicated in the message as the recipient of the communicationmedium, and it has an assignment unit, which is designed for assignmentof the communication medium to the at least one other terminal as therecipient of the communication medium.

One aspect of the invention can clearly be considered to be that ofrequesting the media replication by means of a message which specifies aplurality of receivers.

In particular, the invention also has the advantageous effect that itallows media to be replicated to a plurality of appliances in a givencollaborative communication session, as well as an IMS collaborativesession, thus allowing a specific medium no longer to be received onlyby a single appliance, which is involved in the collaborative session,but by a plurality of appliances in the collaborative session.

Only one terminal in a collaborative session can receive a medium whichis received in the course of the collaborative session. The inventionmakes it possible to distribute media received in the course of acollaborative session in a more flexible manner between the terminalsinvolved in the collaborative session.

One effect of the invention can clearly be considered to be that ofallowing media to be copied in the collaborative communication session,as a result of which the relevant media are received by a plurality ofterminals involved in the collaborative communication session.

Further exemplary embodiments of the invention can be found in thedependent patent claims and in the following description. In this case,where applicable, the explanations relating to the methods also relatein the same sense to the apparatuses, and vice versa.

According to one exemplary embodiment of the invention, the message issent by a terminal.

According to one exemplary embodiment of the invention, the message issent by a terminal which is currently not assigned a control role forthe collaborative communication session.

According to one exemplary embodiment of the invention, the message isreceived by a server in a communication system, and the communicationmedium is assigned by a server in the communication system.

According to one exemplary embodiment of the invention, thecommunication medium is copied by a server in the communication system,and the copied communication medium is distributed to the at least oneterminal and the at least one other terminal by a server in thecommunication system.

According to one exemplary embodiment of the invention, a server in thecommunication system produces a direct media connection, which issuitable for transmission of the communication medium, between the atleast one other terminal as the recipient of the communication mediumand a terminal which sends the communication medium.

According to one exemplary embodiment of the invention, the at least oneother terminal includes a plurality of terminals, that is to say aplurality of other terminals may occur instead of at least one otherterminal, for example two, three, four, five or even more otherterminals. The message relating to media replication includes aplurality of other terminals, that is to say it states a plurality ofterminals which occur instead of the at least one other terminal, forexample two, three, four, five or even more other terminals. This hasthe advantageous effect that media replication can be requested by meansof a single message at more than one additional recipient, specificallyfor example two or more additional receiving terminals, that is to say atotal of more than two terminals that receive the medium. This savessignaling complexity.

According to one exemplary embodiment of the invention, the messageindicates the at least one terminal as the recipient of thecommunication medium.

According to one exemplary embodiment of the invention, the message isformed on the basis of the Session Initiation Protocol (SIP), and itsmessage type REFER. One aspect of the invention can clearly beconsidered to be that of the media replication being requested by meansof an SIP-REFER message which specifies a plurality of recipients.

According to one exemplary embodiment of the invention, the SIP-REFERmessage specifies all the receivers for which reception of the medium orof the media is requested.

According to one exemplary embodiment of the invention, the media to becopied can be identified in an SIP-REFER message with which mediareplication is requested, for example by means of media identifiers, forexample the call identification (call-ID) of the communication sessionassociated with the media, a header field (to-header) which indicates anaddressee of the message, a header field (from-header) which indicates asender of the message, and/or a description based on the SessionDescription Protocol (SDP). In an SIP message, media can be described inaccordance with the SDP in the message body of the SIP message.According to SDP, media can be marked by means of an SDP markingattribute (label attribute), and can thus be identified.

According to one exemplary embodiment of the invention, an SIP-REFERrequest is sent to a server in the communication system. A server in thecommunication system matches existing media (media connections, mediaflows) to the received media identifiers, for example received SDPmarking attributes, and sets up appropriate media connections to all therequested recipients. A server in the communication system then receivesand copies the media, and distributes them to the recipients. Mediareplication by means of a server in the communication system has theadvantage that, in the case of those terminals which send the media,transmission bandwidth is saved in comparison to the situation in whichthey had to send multiple copies of the media, thus saving transmissionbandwidth overall in the communication system.

According to one exemplary embodiment of the invention, a server in thecommunication system sets up direct media connections between theterminals involved, that is to say in each case between the sendingterminal and the various terminals which receive the medium. In thiscase, the medium is copied by the sending terminal.

According to one exemplary embodiment of the invention, the apparatusfor requesting media replication is furthermore configured to carry outthe method according to one of the exemplary embodiments which relate tothe method for requesting media replication.

According to one exemplary embodiment of the invention, the apparatusfor assignment of a communication medium is furthermore configured tocarry out the method according to one of the exemplary embodiments whichrelate to the method for assigning a communication medium.

According to one exemplary embodiment of the invention, the terminalwhich sends the message is designed for access to a communicationsystem, and the message is sent to a server in the communication system.

According to one exemplary embodiment of the invention, thecommunication system is a communication system designed in accordancewith the Internet Protocol Multimedia Subsystem (IMS) to the 3GPP mobileradio standard.

Exemplary embodiments of the invention will be explained in more detailin the following text, and are illustrated in the figures, in which:

FIG. 1 shows an architecture, illustrated in a simplified form, of anIMS-based communication system;

FIG. 2 shows a message flowchart, illustrating the message flow formedia transfer within a collaborative session;

FIG. 3 shows a message flowchart, illustrating the message flow forrequesting media replication in a collaborative session, and the messageflow for assignment of a communication medium for a collaborativesession, according to exemplary embodiments of the invention;

FIG. 4 shows a message flowchart, illustrating the message flow forrequesting media replication in a collaborative session, and the messageflow for assignment of a communication medium for a collaborativesession, according to other exemplary embodiments of the invention; and

FIG. 5 shows a flowchart illustrating a method for requesting mediareplication in a collaborative session, and a method for assignment of acommunication medium for a collaborative session according to exemplaryembodiments of the invention.

For the purposes of this description, the terms “linked”, “connected”and “coupled” are used to describe both a direct and an indirect link, adirect or an indirect connection and a direct or indirect coupling.Identical or similar elements are provided with identical referencesymbols in the figures, where this is expedient.

Exemplary Embodiment 1

A communication system is considered, which is based on the InternetProtocol Multimedia Subsystem (IMS) to the 3GPP mobile radio standard.

FIG. 1 shows an architecture, illustrated in a simplified form, of anIMS-based communication system 100.

The communication system 100 consists of terminals and servers, to whichthe terminals are connected. In order to simplify the illustration, allof the relevant servers are referred to in a summarized form as IMSservers 105 (S, server) in the following text. In real systems, the IMScontains a multiplicity of servers with specific functionalities, forexample a call session control function server, an application server,etc.

In the example, three communication terminals T1 110, T2 115 and T3 120are associated with one user U1. A further terminal T4 125 is associatedwith the user U2. All of the terminals are connected to the IMS server105 and are registered with the server 105, as is symbolized bydouble-headed arrows 130.

The communication control in IMS is set up using the Session InitiationProtocol (SIP). An SIP REFER message, that is to say a message of theREFER message type, can be used by one communication appliance torequest communication session control messages for another communicationappliance. In IMS collaborative sessions, SIP REFER messages are used inorder to transfer media transmission from one terminal to anotherterminal.

FIG. 2 shows a message flowchart, illustrating the message flow formedia transfer within a collaborative session in the IMS-basedcommunication system 100 as shown in FIG. 1.

The user U2 uses his terminal T4 125 to call the terminal T2 115 of userU1 by means of the SIP INVITE message 205, of the INVITE message type.U1 accepts the call with his terminal T2 115, and T2 115 confirms theacceptance by means of the confirmation message OK 210. T2 is a mobiletelephone. Subsequently U1 arrives at home, where he wishes to take partin a call with his wife. U1 wishes to make the call using the stationaryappliance T1 110 (for example a computer) and therefore transfers theaudio data for communication with T4 125 from his mobile telephone T2115 (previous audio connection 215 between T2 and T4) to his computer T1110.

T2 115 uses an SIP REFER message 220 to request the transfer of themedia data from T2 115 to T1 110. The SIP REFER message 220 which issent may appear as shown in the following Table 1 (the table shows onlya small number of message fields which are relevant for the explanationin conjunction with the invention):

Request-URI S SIP HEADERS To: S From: T2 Refer-to: T1; method=INVITEContact: T2

In this case, S is the SIP address of the IMS server 105, which is inthis case stated in the form of an Internet address, that is to say aUniform Resource Identifier (URI). T1 and T2 are the SIP addresses ofthe subscriber terminals T1 110 and T2 115, respectively.

The server 105 uses the message ACCEPTED 225 to accept the mediatransfer request. The server 105 now uses the INVITE message 230 toinvite T1 110 to join the audio communication, and T1 110 confirms thisby the confirmation message OK 235. The server 105 then uses there-INVITE message 240 to inform T4 125 about the new audio connectionand T4 125 confirms this by means of the confirmation message OK 245.Finally, the server 105 uses the re-INVITE message 250 to inform T2 115of the completion of the media transfer, that is to say the originalinvitation to T2 is now changed to an invitation without a mediaconnection “no media”, and T2 115 confirms this by means of theconfirmation message OK 255.

The request for the media transfer by the terminal T2 115 results in acollaborative session with a new audio connection 260 between T1 110 andT4 125. “Controller=T2” 265 is used to assign the control role for thecollaborative session to T2 115. By way of example, this means that T2115 can subsequently carry out further media transfers.

FIG. 3 shows a message flowchart, illustrating the message flow forrequesting media replication in a collaborative session, and the messageflow for assignment of a communication medium for a collaborativesession according to exemplary embodiments of the invention.

This process starts from the situation at the end of the messageflowchart in FIG. 2, that is to say a collaborative session exists withan audio connection 260 between T1 110 and T4 125, with T2 115 beingassigned the control role for the collaborative session.

The user U1 now wishes to leave his computer. In order to allow his wifeto continue to hear the call and to allow him himself to still take partin the call, the user U1 now wishes to replicate the audio connection(the audio medium flow) to his mobile telephone T2 115 (copy, model,replicate), that is to say to initiate media replication of the audiomedium in the collaborative session to his mobile telephone T2 115 as afurther recipient.

U1 requests the media replication with T2 115 as follows:

T2 115 first of all uses the SIP SUBSCRIBE message 305, which is of theSUBSCRIBE message type, to request information from the IMS server 105about the collaborative session, including identification informationrelating to the medium to be transmitted (in this case an audio stream),for example media identifiers, which the server 105 first of allconfirms by means of the confirmation message OK 310. The server 105then sends the SIP NOTIFY message 315, which is of the NOTIFY messagetype and contains the information relating to the medium to betransmitted, to T2 115. T2 115 uses the confirmation message OK 320 toconfirm reception of the message 315.

According to the exemplary embodiment of the invention, T2 115 thensends an SIP REFER message 325 to the IMS server. The SIP REFER message325 which is sent may appear as shown in the following Table 2 (thetable shows only a small number of message fields which are relevant forthe explanation in conjunction with the invention):

Request-URI S SIP HEADERS To: S From: T2 Refer-to:cid:Example-Internet-Address; method=INVITE; Request-URI=<T2>; To=<T2>;From=<T4>; Call-ID=<Example-Call-Identification>; Contact=<T4> Contact:T2 Content-Type: application/resource-lists+xml Content- recipient-listDisposition: Content-Length: . . . Content-ID:<Example-Internet-Address> BODY . . .  <resource-lists> . . .   <list>   <entry uri=T1/>    <entry uri=T2/>   </list>  </resource-lists>

In this case, S is the SIP address of the IMS server 105, which in thiscase is stated in the form of an Internet address, that is to say aUniform Resource Identifier (URI). T1 and T2 are the SIP addresses ofthe subscriber terminals T1 110 and T2 115, respectively.

The message 325 indicates that the medium which is currently beingreceived by T1 110 (is transmitted to T1) should in future betransmitted both to T1 and to T2 115, that is to say it should in futurebe additionally transmitted to T2.

The message 325 identifies the audio medium received by T1 110 on thebasis of the call identification for the collaborative session, that isto say the indication “Call-ID=<Example-Call-Identification>”.

The fact that the message 325 specifies media replication withsubsequent reception of the medium both by T1 110 and by T2 115 as well,is evident from the statement “cid:Example-Internet-Address” in the“Refer-to:” field of the message 325. This is because the“Example-Internet-Address” refers to a list in the “BODY”, in which bothT1 and T2 have been entered.

The server S 105 receives the message 325 and accepts the request formedia replication using the ACCEPTED message 330.

The server S 105 matches the media identifiers contained in the receivedmessage 325 with the existing audio media stream (audio connection 260),which is used by T1 and T4. The server finds that the audio medium is atthe moment being transmitted at the end for the user U1 to T1 110, butshould in future also be transmitted to T2 115.

The server assigns the audio medium to T2 115 as an additional recipientfor this medium at the end for the user U1. The server S 105 then setsup new media connections, specifically the audio connection 385 betweenT1 110 and the server S 105 (by means of the messages 335 and 340), theaudio connection 390 between T2 115 and the server S 105 (by means ofthe messages 345 and 350) and the audio connection 395 between T4 125and the server S 105 (by means of the messages 355 and 360).

Once the new media connections (audio connections 385, 390, 395) havebeen set up, the server S 105 sends a further SIP REFER message 365 toT4 125, in which T4 uses the reference method BYE (clearance) to requestclearance of the direct media connection between T1 110 and T4 125, thatis to say the audio connection 260. The SIP REFER message 365 sent bythe server may appear as shown in the following Table 3 (the table showsonly a few message fields which are relevant for the explanation inconjunction with the invention):

Request-URI T4 SIP HEADERS To: T4 From: S Refer-to: T1; method=BYEContact: S

In this case, S is the SIP address of the IMS server 105, which is inthis case indicated in the form of an Internet address, that is to say aUniform Resource Identifier (URI). T1 and T4 are the SIP addresses ofthe subscriber terminals T1 110 and T4 125, respectively.

T4 125 uses the message OK 370 to confirm the request to clear the audioconnection 260. The direct media connection between T1 110 and T4 125 isended with the message BYE 375 (clearance) and OK 380. The server S 105then receives the audio data from T4 via the audio connection 395,copies it (replicates it), and distributes it via the audio connections385 and 390 to T1 110 and T2 115.

The terminal T2 115 has a transmitting unit 3010, which is designed tosend the message 325, which specifies that the audio medium for thecollaborative communication session at the end for the user U1 isintended to be transmitted not only to T1 110, as in the past, butadditionally to T2 115 as well.

The server S 105 has a receiving unit 3020, which is configured toreceive the message 325, and it has an assignment unit 3030, which isconfigured to assign the audio medium for the collaborativecommunication session at the end for the user U1 to the terminal T2 115,which is specified in the message 325 as an additional recipient for theaudio medium.

Exemplary Embodiment 2

FIG. 4 shows a message flowchart, illustrating the message flow forrequesting media replication in a collaborative session, and the messageflow for assignment of a communication medium for a collaborativesession, according to other exemplary embodiments of the invention.

This example starts from the situation at the end of the messageflowchart in FIG. 2. A collaborative session therefore exists with anaudio connection 260 between T1 110 and T4 125 (the terminal T1 for theuser U1 is communicating with the terminal T4 of the user U2). T2 115has been assigned the control role for the collaborative session.

As in exemplary embodiment 1, the user U1 now wishes to replicate theaudio connection (the audio media stream) to his mobile telephone T2 115(copy, model; replicate), that is to say to replicate the media from theaudio medium in the collaborative session to his mobile telephone T2 115as a further recipient.

The media replication is requested by T2 115, and the server S 105accepts the request for media replication by means of the messages 305,310, 315, 320, 325 and 330, in the same manner as in exemplaryembodiment 1. The messages 305, 310, 315, 320, 325 and 330 have beenexplained in more detail above during the course of the descriptionrelating to FIG. 3. The SIP REFER message 325 can likewise appear as isshown in Table 2, shown above, and will be explained in more detail withreference to this table.

The server S 105 matches the media identifiers contained in the receivedmessage 325 with the existing audio media stream (audio connection 260),which is used by T1 and T4. The server finds that the audio medium atthe end for the user U1 is presently being transmitted to T1 110, but infuture should also be transmitted to T2 115. The server assigns theaudio medium to T2 115 as an additional recipient of this medium at theend for the user U1.

Since the server S 105 has previously (see the description relating toFIG. 2) set up the direct audio connection 260 between T1 110 and T4125, it knows that this connection already exists. In this exemplaryembodiment, the server therefore does not set up a new media connectionbetween T1 and T4 running via the server. In addition, no new mediaconnection running via the server is set up between T2 and T4.

Instead of this, the server S 105 merely sets up a direct new audioconnection 405 between T4 125 and T2 115. An SIP REFER message 410,which requests T4 to call T2, is used to request the audio connection405.

The SIP REFER message 410 that is sent may appear as is shown in thefollowing Table 3 (the table shows only a small number of messagefields, which are relevant for the explanation in conjunction with theinvention):

Request-URI T4 SIP HEADERS To: T4 From: S Refer-to: T2; method=INVITEContact: S

In this case, S is the SIP address of the IMS server 105, which is inthis case indicated in the form of an Internet address, that is to say aUniform Resource Identifier (URI). T2 and T4 are the SIP addresses ofthe subscriber terminals T2 115 and T4 125, respectively.

T4 125 receives the message 410, and accepts the request for the audioconnection 405 using the message ACCEPTED 415. T4 125 now invites T2 115to join the audio communication, using the INVITE message 420, and T2115 confirms this by means of the confirmation message OK 425.

The two audio connections 260 and 405 then exist in the collaborativecommunication session. Both T1 110 (as prior to this) and T2 115 (nowadditionally) receive the audio medium in the collaborativecommunication session at the end for the user U1.

Further Exemplary Embodiments

FIG. 5 shows a flowchart 500, illustrating a method for requesting mediareplication in a collaborative communication session, and a method forassigning a communication medium for a collaborative communicationsession, according to exemplary embodiments of the invention. Theexemplary embodiments illustrated in FIG. 5 can be combined with all theother described exemplary embodiments of the respective method.

First of all, a method will be described for requesting mediareplication in a collaborative communication session, based on oneexemplary embodiment of the invention.

In 510, a message is sent which specifies that a communication mediumfor a collaborative communication session, which is currently beingtransmitted to at least one terminal, should be additionally transmittedto at least one other terminal, with the at least one other terminalbeing stated in the message as a recipient of the communication medium.

A method will now be described for assigning a communication medium fora collaborative communication session according to one exemplaryembodiment of the invention:

In 520, a message is received which specifies that a communicationmedium for a collaborative communication session, which is currentlybeing transmitted to at least one terminal, should additionally betransmitted to at least one other terminal, with the at least one otherterminal being indicated as a recipient of the communication medium inthe message.

In 530, the communication medium is assigned to the at least one otherterminal as a recipient of the communication medium.

In the overall analysis, 510, 520 and 530 indicate the interaction ofthe method for requesting media replication in a collaborativecommunication session and the method for assignment of a communicationmedium for a collaborative communication session at the system level oroverall network level.

According to one exemplary embodiment, the invention may also be usedfor collaborative sessions which include the terminals of a plurality ofusers, that is to say in which a plurality of users with a plurality ofterminals form one of the communication ends.

According to one exemplary embodiment, the invention may also be usedfor requests for media replications by controlled terminals, that is tosay non-controlling terminals. In this case, the message which requestsmedia replication is not sent by a controlling terminal, that is to sayby a holder of the control role for the collaborative communicationsession, but by a terminal which does not, or does not at the moment,have the control role for the collaborative communication session. Thismakes it possible to control a collaborative session in a particularlyflexible manner.

According to one exemplary embodiment, in the situation in which anon-controlling (controlled) terminal requests media replication, it ispossible to assign the requesting non-controlling terminal a controlrole for the collaborative communication session, or to automaticallyassign this. Alternatively, the requesting terminal can remain acontrolled terminal. If the requesting terminal is assigned a controlrole, it is also possible for already existing controlling terminals toremain in this role. Alternatively, it is also possible for alreadyexisting controlling terminals to lose their control roles, that is tosay they become terminals to be controlled (control role transfer).

According to one exemplary embodiment, it is possible for a server inthe communication system to authorize media replication which isrequested by a controlled terminal. For example, this can be authorizedby existing controlling terminals being asked for authorizationpermission. The controlling terminals can then ask their users forpermission.

According to one exemplary embodiment, instead of a list with therespective SIP-URI of the respective media recipients, a reference to anexternal SIP-URI list may be contained in the SIP REFER message, in thecase of an SIP-REFER message for requesting media replication.

According to one exemplary embodiment, media can be identified by SDPmarking attributes. In this case, the server matches existing media(media connections, media streams) with the received SDP markingattributes.

According to one exemplary embodiment, the invention can be used toreplicate media at more than two destination terminals (copying). Inthis case, the recipient list for the replication request may containmore than two SIP-URIs.

According to one exemplary embodiment, the invention can also be usedwhen a communication control protocol other than SIP is being used,and/or when a communication system other than IMS is being used.

1. A method for requesting media replication in a collaborativecommunication session, the method comprising: sending a message whichspecifies that a communication medium for a collaborative communicationsession, which is currently being transmitted to at least one terminal,should additionally be transmitted to at least one other terminal, withthe at least one other terminal being indicated in the message as therecipient of the communication medium.
 2. The method as claimed in claim1, wherein the message is sent by a terminal which is currently notassigned a control role for the collaborative communication session. 3.A method for assigning a communication medium for a collaborativecommunication session, the method comprising: receiving a message whichspecifies that a communication medium for a collaborative communicationsession, which is currently being transmitted to at least one terminal,should additionally be transmitted to at least one other terminal, withthe at least one other terminal being indicated in the message as therecipient of the communication medium; and assigning the communicationmedium to the at least one other terminal as the recipient of thecommunication medium.
 4. The method as claimed in claim 3, wherein themessage is received by a server in a communication system, and thecommunication medium is assigned by a server in the communicationsystem.
 5. The method as claimed in claim 4, further comprising: copyingthe communication medium by a server in the communication system; anddistributing the copied communication medium to the at least oneterminal and to the at least one other terminal by a server in thecommunication system.
 6. The method as claimed in claim 4, furthercomprising: setting up a direct media connection, which is suitable fortransmission of the communication medium, between the at least one otherterminal as the recipient of the communication medium and a terminalwhich sends the communication medium, by a server in the communicationsystem.
 7. The method as claimed in claim 1, wherein the at least oneother terminal includes a plurality of terminals.
 8. The method asclaimed in claim 3, wherein the at least one other terminal includes aplurality of terminals.
 9. The method as claimed in claim 1, wherein themessage indicates the at least one terminal as the recipient of thecommunication medium.
 10. The method as claimed in claim 3, wherein themessage indicates the at least one terminal as the recipient of thecommunication medium.
 11. The method as claimed in claim 1, wherein themessage is formed on the basis of the Session Initiation Protocol (SIP),and its message type REFER.
 12. The method as claimed in claim 3,wherein the message is formed on the basis of the Session InitiationProtocol (SIP), and its message type REFER.
 13. An apparatus forrequesting media replication in a collaborative communication session,the apparatus comprising: a transmitter configured to send a messagewhich specifies that a communication medium in a collaborativecommunication session, which is currently being transmitted to at leastone terminal, should additionally be transmitted to at least one otherterminal, with the at least one other terminal, being indicated in themessage as the recipient of the communication medium.
 14. The apparatusas claimed in claim 13, furthermore configured to carry out a method forrequesting media replication in a collaborative communication session,the method comprising: sending a message which specifies that acommunication medium for a collaborative communication session, which iscurrently being transmitted to at least one terminal, shouldadditionally be transmitted to at least one other terminal, with the atleast one other terminal being indicated in the message as the recipientof the communication medium.
 15. An apparatus for assigning acommunication medium for a collaborative communication session, theapparatus comprising: a receiver configured to receive a message whichspecifies that a communication medium for a collaborative communicationsession, which is currently being transmitted to at least one terminal,should additionally be transmitted to at least one other terminal, withthe at least one other terminal being indicated in the message as therecipient of the communication medium; and an assignment circuitconfigured to assign the communication medium to the at least one otherterminal as the recipient of the communication medium.
 16. The apparatusas claimed in claim 15, furthermore configured to carry out a method forassigning a communication medium for a collaborative communicationsession, the method comprising: receiving a message which specifies thata communication medium for a collaborative communication session, whichis currently being transmitted to at least one terminal, shouldadditionally be transmitted to at least one other terminal, with the atleast one other terminal being indicated in the message as the recipientof the communication medium; and assigning the communication medium tothe at least one other terminal as the recipient of the communicationmedium.